Signal-receiving circuits



1 624,148 Aprll 12 1927. E. L. POWELL 4 i, l

' SIGNAL RECEIYING CIRCUITS Filed March 6,' 1926 INVENTOR.

EMME/gag?, Z. we Z Patented Apr. 12, 1927;

siren l STATES PATENT oFFlCE. l

EDWIN L. POWELL, OF WASHINGTON, DISTRICT OF COLUMBIA, .AS-SIGNOR- TO WIRED RADIO, INC., OF NEW YORK, N. Y., vA CORPORATION OF DELAWARE.

SIGNAL-RECEIVING CIRCUITS.

Application flied March 6, 1926. Serial No. 92,893.

My invention relates broadly to signal receiving circuits andmore particularly to electron tube circuits having means forA controlling the degree of feedback between the plate and grid circuits of -an autodyne tube. One ofthe objects o f my invention is to provide a system for automatically stabilizingautodyne tube circuitsjin signal receiv- --ing systems to prevent powerful signals or static impulses from throwing the circuitl previously adjusted to peak regeneration, into the condition of self-oscillation. Another object of my invention 1 s to pro- A-vide an automatic govei'nor.'systemV for electron tube circuits of the autodyne 4type for keeping the regenerative feedback at a predetermined constant value through the range vof the grid circuit tuning means regardless'fof the variations in the grid circuit resistance resultant from such tuning.

Still anotherobject of my inventionv is `to provide an electron tube system of the autodyne type in which the feedback between the plate and grid circuits can be adjusted to the desired degree of regeneration or self-oscillation with a mjnimum-`of reaction of the regenerative'control variai tion on the resonant frequencyhofthe tuned with dual means for both regeneratin and degenerating with .respect to the gri circuit; and whereby, with a single nonreactive control, a balance may .be secured between the two means for any desired resultant` degree of regeneration, said balance being automatically maintained independent of variationsin the inherent resistance of or the voltage applied to the grid circuit.

.Other and further objects of my invention 'will be understood from the following specification by reference to the accon'ipay-v ing drawings, wherein:

Figure 1 isa diagrammatic view showing an electron tube circuit arranged 1n accord- -ance with my invention wherein a noniiiductive potentiometer is em loyed for the regeneration controlmeans; ).Pi 2 shows a similar arrangement in which t e radio frequency and direct current paths to the plate are in parallel; Figs. 3 and 4 show, other forms of series and parallel feed systems utilizing capacity control for regeneration in' accordance with my invention; `and Figs. '5 and 6 show series and arallel feed sys# tems employing the varia lel couplin type ofgreg'enerative control for electron tu e circuits constructed in accordance with my invention. l

In electron tube amplification or rectifica- 'l tion circuits used in signal receiving'systems .-of damped or modulated continuous waves,

greatest sensitivity to weak ofr distant signals is had when the regeneration is inoscillations begin. Likewise, in the reception of continuous wave telegraph signals by the autodynemethod,' which consists of oscillating thedetector at a frequency sli htly oli resonance from the desired signa so t at an audible beat frequency is produced, greatest sensitivity. is secured when the 1ocal oscillations are the weakest. In either case, the circuits are most critical when so adjusted and their sensitivity is subject to considerable variation, if not to complete loss of reception by reason of the circuit go? ing over from the regenerating to the oscillating condition or vice versa, either as a re-y sult of powerful applied signal or static voltages or merely as a result of the varia- 'creased to the peak value, or just before selftion 1n grid circuit losses which occur in,

tuning. Thus,'in the normal circuits previously known to the art, it has been necesthat is, the resultant effect is equivalent to.

an increase in the resistance of the grid circuit. lln ,my invention l provide a degenerating tickler coil toincrease the grid circuitresistance appreciably above its inherent value and then Supply a regenerative ticklerl capable of supplying sufiicient negative resistance to neutralize thecombined edect of the two'. I further provide a single means of controlling the magnetic fields set up4 by the two tickler coils whereby the strength of. one is increased as that of the other is-decreased, so that the resultant effective field may be adjusted to produce any degree of regeneration or oscillation desired. Then, by reason of'itsdifferential action, any variation in the grid circuit causes a corresponding change in both phases of the plate feedback circuit, providingI a governor effect which stabilizes the systeinin the condition adjusted. Thus, once adjusted to peak regeneration or minimum oscillation as. de-

' sired, my circuit remains always in the most sensitive condition and the regeneration co'ntrol device requires no further attention regardless of the strength of received impulses or manipulation of the capacity of the grid circuit tuning condenser. My circuit arrangement is both applicable to amplification and rectification, and in order to explain one of its preferred embodiments T have illustrated several methods of operating an electron tube rectification system in accordance with the principles of my invention.

Referring to the drawings in more'detail, I have shown in Fig. 1 a resistance controlled circuit with series feed connection to the plate. Reference character 1 designatesv the'grid inductance and 2 the variable condenser which constitute the tuned input circuit to the electr'm tube detector 4 and which may be energized by a radio antenna system, wired radio conductor, radiofrequency amplifier coupling coil or the like. '3 is a stoppin condenser in the grid lead to the tube 4, siunted by grid leak 3a. The filament of tube 4 is heated by the battery 10, the current being controlled by the rheostat 21. 5 is the dual tickler coil. which is wound in fixed relation to thegrid indue-, tance and has somewhat'more than twice the number of turns normally required to martine produce oscillations through the frequency range of the grid circuit, a taprll near the center of` the winding connecting to the plate of the electron tube 4, and the outside endsfof the inductance connected across the c resistance of the non-'inductive potentiometer 6. The sliding contact 15 of the potentionieter completes the plate circult through the telephone 7 (o1-` audio frequency transformer' primary) andfhighpotential battery S, to the` filament, hothofwhich are geiierates while the other dcgcneratcs; thcr strength 'of the field of one phasevai'ying inversely to thatl of the opposite phase as the potentiometer slider 15 is moved from one end of the resistance to the other. @nce adjusted for a desired degree of feedback, the ratio of thc two fields will remain practically constant regardless ot' fluctuations in the total plate current, whether causedV by variations either in circuitlosses, orapplied grid voltage (signal energy). Thus the potentiometer adjustment for.` peak regeneration or minimum oscillation, once made for any given setting of the grid circuit tuning condenser, will be constant .for all settingsl of the tuning condenser and the complete system willv remain stable regardless of .the

strength of signals to which it is made resonant. The fixed coupling lfeature between plate and grid inductances with separate rcgeneration control means, which lgives a constant mutual inductance between the two circuits and, therefore, eliminates considerable of the reaction on circuit frequency which was experienced previously in circuits employing variable coupling for regeneration adjustment, is covered by my copending application Serial No. 643,993, for high frequency electrical circuits, filed 'J une 7, 1923. This reaction of the regeneration control adjustment on the grid circuit frequency is still further reduced by my present invention since the total plate circuit impedance for a given frequency, remains essentially constant throughout'the useful range of the potentiometer. I

Various arrangements areshown in the remaining figures, like reference numerals being used throughout for corresponding arts. Fig. 2 also shows a resistance control ut in this arrangement the direct and audio frequency vcurrents are fed -to the plate through a radio frequency choke 11,1a parallel lfeed for the radio frequency current being employed. Figs. 3 and 4 show series and parallel feed systems respectively using In operationgthc plate capacitive control ofregeneration, wherein a variable condenser 12 having two sets of stator plates and operates in conjunction with oi e rotorsystem 18- to'increase the capacitivei r'eactance in .one leg of tlie"-tickler system as `it is' decreased-in the.

other. Figs. /5 Vand 6 represent series and parallel feed systems respectively, but in these two cases the control is by variable coupling at 13, under which condition two oppositely wound tickler coils 19 and 2() set 90 degrees to each other and connected in parallel ai'e arranged to permit rotation through an angle ot 90 degrees Witlrrespect to the grid inductance I, thereby increasingthe regenerative feedback as degeneration diminishes and vice versa.

In practical operation of inyinveiition, I have carefully investigated the merits of the' balance winding system with th'e degenerating Winding open and closed. Vith'the A degenerating winding open, oscillations were obtained when the tuning condenser was set -at maximum with regeneration control at ll() degrees, but when the condenser was re-l duced to the minimum setting, degrees of the regeneration control was" required,

-the gradation for intermediate values being fairly constant between the two limits.

With the balancewinding connected in, oscillations were obtained at degrees of regeneration throughout the range of the tun# ing condenser. Set to peak regeneration with no4 applied signal, nooscillationswere developed when the local station was tuned 1n.

` made and that no limitations upon the invention are intended other than those iniposed by the scope of the appended claims.

What I claim and desire to secure by Letters Patent of the United States is as fol- 1. An electron tube system comprising in Y combination with an electron tube having grid,l filament and plate electrodes, an input circuit including said grid and filament electrodes, an output circuit including said plate andfilament electrodes, and a difierential circuit interlinking said input -and output circuits comprising an inductance shuntedby an impedance, said impedance Without the balancing Winding and. with the receiver located at Washington, D. C.,station KFI in California could not be received because of strong static dis-- tion.

becoming increasingly large in one portioieof saldi differential circuit While said uur.

pedance decreases in another portion of said. differential circuit -one oition of said dii`- ferential .circuit operating to facilitate/,ite-

generation in said circuits, and another portion `of said differential circuit operating toreduce the tendency of said circuits to regenerate, whereby a balanced condition of opleiation of said circuits may be maintained in,

a predetermined state of regeneration or oscillation. l

2. An electron tube system comprising in combination with an electron tube having. grid, filament and plate electrodes, aninput circuit including said grid and filament electrodes. an output circuit including saidplate and filament electrodes, an inductance located in each-of said circuits, the inductance. in said output circuit having4 a midpoint thereof connected with said plate electrode, a resistance shunted across saidlast named inductance and having a variable connection extending between said resistance and said output circuit, whereby the state of regeneration or oscillation in said circuits may be manually adjusted and automatically maintained. l Y f '3. In an electron tube system the combination. with an electron tube having giiid, fila'nent and plate electrodes, input and output circuits interconnecting said electrodes,

a balance circuit including an in'ductance device shunted b a resistance, a connection between th'e .ini point of saidinductance and circuit and being relatedlto said input circuit in such manner that said circuit tends vto govern the regenerative properties of said electron tube system and maintaimsaid electron tube system in a substantially constant condition of regeneration or oscilla- 4. In an electron tube system, the combi-` IIN) l saidplate electrode, said inductance and rcsistance, being interposed in said output nation of an electron tube having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes, a

Abalancecircuit connected in said output circuit, said balance circuit havin one point thereof connected to said platee ectrode and having means connected across the opposite ends thereof and variably associated with a point in said output circuit for governing the regenerative action of said electron tube circuits.

ment and plate electrodes, input and output circuits interconnecting said electrodes, an

Ainductance device included in each of said circuits, the inductance device in said output circuit being connected in a balance circuit with a connection between a midpoint 'of said last mentioned inductance device 5. In an electro tube system the eombinal tion of an electron tube having grid, lila- I and said plate elect-rode, and means connectof regeneration or oscillation.

ed across said balance circuit for variablyincreasing or decreasing the regenerative properties of said electron tube circuits, said balance circuit maintaining said electron tube circuits in a predetermined 'constant state of regeneration or oscillation.

6. In an'electron tube .system the combination of an electron tube havin-g grid, filanient and plate electrodes, input and Aoutput circuits interconnecting said electrodes, an inductance device included in each of said circuits, the inductancedevice in said outputl circuit being connected in a balance circuit, and an impedance in shunt with said -inductance device arranged to be variably increased in one of said circuits at the same rate that it is decreased in another of said i circuits for variably increasing or decreasingthe tendency of said balance circuit to regenerate, whereby said electron tube circuits are maintained constantly i indesired state 7. In an electron tube systein the coin-bi- .natiou of an electron tube having grid, fila- `ment and plate electrodes, input and outincantati filament andplate electrodes, an input circuit including said grid and filament electrodes, an output circuit including said plate and lament electrodes, an inductance device interposed in each of said circuits and magnetically associated, the inductance device in said output circuit being arranged in. a differential circuit with an intermediate point of said inductance device coni nccted with said plate electrode, thereby dividing said inductance device into two portions having fields of opposite phase, whereby one portion tends toinc'rease' the regenerative condition of'4 said electron tube circuits, while the other portion tends to decrease the regenerative properties of said electron tube circuits, yand a single means associafedwith the extremities of said output circuit inductance for adjusting said electron` tube circuits to a desired resultant state of' regeneration or oscillation' which increases the magnetic field set up in one portion of said output circuit inductancc inversely as it decreases the/magnetic field putcircuits interconnecting said electrodes,

an inductance device included inA each of said circuits, a balance circuit connected in said output circuit and including in series therewith the inductance device of said output circuit, said last mentioned inductance device being divided into two portions and having means connected across each portion' for increasing and decreasing the tendency of said electron tube circuits to regenerate, whereby said electron tube circuits may be maintained constantly in a` predetermined state of regeneration or oscillation.

,8. an electron tube system, the coinbination with aniielectron tube having grid, filament and plate electrodes, an input cii=,-

cuit including said grid andlilament elec- K trodes, an output circuit including said plate and filament electrodes, an inductance device interposed in each of said circuits, the inductance device in said outptfcircuit being arranged in a balancel circuit with a midpoint of'said. last named induetance device connected. with* said plate electrode thereby dividing said inductance device iny to two portions, and means for adjusting said balance circuit, whereby one portion CII of said last named inductance'device tends to increase the regenerative condition of' said electron tube circuits, while the other 'I portion of said last `mentioned inductance idevice tends to ldecrease the regenerative properties of said electron tube circuits, whereby a ycondition of balance may be obtained for maintaining said electron tube circuits constantly in a 'desired state of regeneration or oscillation. A

9. In an electron tube system, the combination with an electron tube having grid,

vin the other portion, saidl differential circuit inaintaining said resultant regeneration at a constant value. a

10. In an electron tube system, the coinbination with an electron tube having grid, filament and plate electrodes, an input circuit including saidV grid and filament electrodes, an output circuit including said plate and filament electrodes, an inductance device interposed in said input circuit, a differentially" connected inductance device consisting of two branch circuits interposed in said output circuit and magneticallycoupled with said inductance device in said iiput circuit, and a Single means inversely a justing the field intensity in the two branches ofsaid differentially connected in ductance device in said output circuit for securing a desired resultant effect on said input circuit, the differential action of said output in'ductance device tending to maintain said adjustment at a constant value.

11. lin an electron tube System, the combination with an' electron tube having grid, filament and plate electrodes, a tuned input circuitincluding said grid and filament electrodes,an output circuit including said plate and filament electrodes, an inductance device comprising a portion of said tuned input circuit, a differentially connected inductance device consisting of two branch circuits, interposed in said output circuit and magnetically coupled with said inductance device in said timed input circuit, the mutual inductance between said inductance device in said Vtuned input circuit and said differentially connected induetance in said output circuit remaining constant by reason of fixed physical relationship2 and a single Y the two branches kof said diicrentially conmeans, s aid constant mutual inductance and vnected inductance in Said output circuit .for said constant output circuit impedance 10 i securing a desired resultant eect on said tendingv to maintain a constant frequency tuned lnput circuit, whereby for a given for said tuned input circuit against varia-v 5 frequency adjustment of said tuned input tions in said regenerative control means.

circuit the lmpedance of said output circuit v In testimony whereof I aix myl signature. f

remains essentially constant through the yuseful range of 'said regeneration control "EDWIN L. POWELL. 

